package com.imooc.trie;

import java.util.TreeMap;

/**
 * 计算以某个字符串为前缀的权重总和
 */
public class MapSum {

    private class Node{
        public int value;
        public TreeMap<Character, Node> next;

        public Node(int value) {
            this.value = value;
        }

        public Node() {
            this(0);
        }
    }

    private Node root;

    public MapSum() {
        root = new Node();
    }

    public void insert(String word, int value) {
        Node cur = root;
        for(int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            if(cur.next.get(c) == null) {
                cur.next.put(c, new Node());
            }
            cur = cur.next.get(c);
        }
        cur.value = value;
    }

    /**
     * 计算以prefix为前缀的权重和
     * @param prefix
     * @return
     */
    public int sum(String prefix) {
        Node cur = root;
        for(int i = 0; i < prefix.length(); i++) {
            char c = prefix.charAt(i);
            if(cur.next.get(c) == null) {
                return 0;
            }
            cur = cur.next.get(c);
        }

        // 计算以cur为根节点的所有单词的权重
        return sum(cur);
    }

    private int sum(Node node) {
        int res = node.value;
        for(char c : node.next.keySet())
            res += sum(node.next.get(c));
        return res;
    }
}
